For reference, small portable devices containing Iridium-192 are frequently used for on-site NDT weld inspections. NDT inspectors often have a truck full of valuable equipment, they are frequently alone on the job site, and the welds being inspected are usually in remote locations. This is not a rare occurrence and odds are the thief has no idea how thoroughly unlucky they are.

https://www.ndt.com.au/product/qsa-sentinel-iridium-ir-192-s...

https://en.wikipedia.org/wiki/Industrial_radiography